Our treasure of the month: Struvite
The type material of struvite was collected in Hamburg in the 19th century. © LIB, Peters
Unfortunate animals may find our treasure of the month in their bodies, because struvite is one of the minerals that constitute kidney stones. In soils, struvite can form when peat compounds react with excrements. The type material of the mineral is stored in the mineralogical collection of the LIB, after it was first discovered in Hamburg in the mid-19th century. In future, synthetic struvite could become important as a phosphate fertiliser in sustainable agriculture.
Struvite occurs in peaty soils as coffin-shaped, white or yellow-brown crystals of up to three centimetres in size. These crystals dehydrate to form newberyite when exposed to air, turning white as a result. Only when stored under protective atmosphere, such as in the mineralogy exhibition of the Museum der Natur Hamburg, clear struvite crystals remain intact. The mineral has been identified in peaty soils from over 45 locations worldwide, including Australia, the Western Cape of Africa and the USA.
The exhibits are protected in the exhibition by a glass bell. © LIB, Steinkröger
The struvite was first found by archaeologists at the St. Nikolai Church in Hamburg in 1846. It was then described by chemist and politician Georg Ludwig Ulex, who named the mineral after Heinrich von Struve, one of the co-founders of the former Natural History Museum in Hamburg. The mineralogical collection of the Museum der Natur Hamburg contains some of struvite specimens that were discovered at the St. Nikolai Church. “In particular the type specimens, i.e. the first specimens of the mineral that were described by Ulex, are a real treasure in the collection”, says Dr. Stefan Peters, Head of Mineralogy at the Museum der Natur Hamburg.
Struvite often forms on peat, as this find at the Nikolai Church in Hamburg shows. © LIB, Steinkröger
“I am very pleased that struvite is our Treasure of the Month, because this particular mineral has historical meaning for our museum. Not only struvite was found in Hamburg for the first time, it was also named after a key person for the origin of our collections. In fact, visitors of the former Natural History Museum would already have been able to see some of our struvite samples on display,” Peters summarises.
Seen here in the peat: a dehydrated struvite. © LIB, Steinkröger
Struvite consists of equal parts of ammonium, magnesium, and phosphate, as well as six parts of crystal water. Its phosphate content has drawn attention to the mineral in agricultural studies, because the world’s phosphorus reserves are estimated to be depleted in ca. 50 to 100 years from now on. As struvite can artificially be precipitated from wastewater, it may become a crucial substance in the circular economy of phosphorous in future.
